Hydrophobic, functionalized particles

ABSTRACT

The present invention relates to a stable mixture comprising surface-modified particles which are obtained by reacting metal oxide or semimetal oxide particles with at least one compound selected from among silicon-comprising compounds bearing one, two or three alkoxy radicals and at least one solvent, at least one surface-active substance or a mixture thereof, the use of these particles in systems in which they are brought into contact with at least one solvent, where the mass ratio of solvent to modified particle is greater than 500, and also the use of these particles in agglomeration-deagglomeration cycles.

The present invention relates to a stable mixture comprisingsurface-modified particles which are obtained by reacting metal oxide orsemimetal oxide particles with at least one compound selected from amongsilicon-comprising compounds bearing one, two or three alkoxy radicalsand at least one solvent, at least one surface-active substance or amixture thereof, the use of these particles in systems in which they arebrought into contact with at least one solvent, where the mass ratio ofsolvent to modified particle is greater than 500, and also the use ofthese particles in agglomeration-deagglomeration cycles.

Metal oxide and/or semimetal oxide particles which are functionalized onthe surface by means of silicon-comprising compounds are known from theprior art.

WO 2009/059382 A1 discloses, for example, hydrophobic modification ofmineral fillers and mixed polymer systems. According to this document,hydrophobic modification is effected by reaction of the correspondingmineral particles with silanes, for example C₃-C₁₂-alkyltrialkoxysilanes. That the correspondingly hydrophobically modified particlesaccording to WO 2009/059382 A1 are particularly stable in large amountsof solvents, optionally in the presence of surface-active substances, isnot disclosed in this document.

In the light of the prior art, it is thus an object of the presentinvention to provide particles which are hydrophobicized on the surfaceand have a particularly high stability toward large amounts of solventsand/or surface-active substances.

This object is achieved by a stable mixture comprising surface-modifiedparticles which are obtained by reacting metal oxide or semimetal oxideparticles with at least one compound of the general formula (I)

R¹ _(n)—Si(OR²)_(4-n)  (I)

or polysiloxanes of the general formula (II)

where R¹, R², R³, R⁴, R⁹, R¹⁰, a, b, m and n have the followingmeanings:

-   R¹, R²,-   R⁹, R¹⁰ are each, independently of one another, hydrogen, linear or    branched, optionally functionalized C₁-C₃₀-alkyl, linear or    branched, optionally functionalized C₂-C₃₀-alkenyl, linear or    branched, optionally functionalized C₂-C₃₀-alkynyl, optionally    functionalized C₃-C₂₀-cycloalkyl, optionally functionalized    C₃-C₂₀-cycloalkenyl, optionally functionalized C₁-C₂₀-heteroalkyl,    optionally functionalized C₅-C₂₂-aryl, optionally functionalized    C₆-C₂₃-alkylaryl, optionally functionalized C₆-C₂₃-arylalkyl,    optionally functionalized C₅-C₂₂-heteroaryl,-   the radicals R³ are each, independently of one another, hydrogen,    linear or branched, optionally functionalized C₁-C₃₀-alkyl, linear    or branched, optionally functionalized C₂-C₂₀-alkenyl, linear or    branched, optionally functionalized C₂-C₂₀-alkynyl, optionally    functionalized C₃-C₂₀-cycloalkyl, optionally functionalized    C₃-C₂₀-cycloalkenyl, optionally functionalized C₁-C₂₀-heteroalkyl,    optionally functionalized C₅-C₂₂-aryl, optionally functionalized    C₆-C₂₃-alkylaryl, optionally functionalized C₆-C₂₃-arylalkyl,    optionally functionalized C₅-C₂₂-heteroaryl, —OR¹⁷, a unit of the    general formula

-   the radicals R⁴ are each, independently of one another, hydrogen,    linear or branched, optionally functionalized C₁-C₃₀-alkyl, linear    or branched, optionally functionalized C₂-C₂₀-alkenyl, linear or    branched, optionally functionalized C₂-C₂₀-alkynyl, optionally    functionalized C₃-C₂₀-cycloalkyl, optionally functionalized    C₃-C₂₀-cycloalkenyl, optionally functionalized C₁-C₂₀-heteroalkyl,    optionally functionalized C₅-C₂₂-aryl, optionally functionalized    C₆-C₂₃-alkylaryl, optionally functionalized C₆-C₂₃-arylalkyl,    optionally functionalized C₅-C₂₂-heteroaryl, —OR¹⁸, a unit of the    general formula

-   R⁵, R⁶,-   R⁷, R⁸, are each, independently of one another, hydrogen, linear or    branched, optionally functionalized C₁-C₃₀-alkyl, linear or    branched, optionally functionalized C₂-C₃₀-alkenyl, linear or    branched, optionally functionalized C₂-C₃₀-alkynyl, optionally    functionalized C₃-C₂₀-cycloalkyl, optionally functionalized    C₃-C₂₀-cycloalkenyl, optionally functionalized C₁-C₂₀-heteroalkyl,    optionally functionalized C₅-C₂₂-aryl, optionally functionalized    C₆-C₂₃-alkylaryl, optionally functionalized C₆-C₂₃-arylalkyl,    optionally functionalized C₅-C₂₂-heteroaryl,-   the radicals R¹⁵ are each, independently of one another, hydrogen,    linear or branched, optionally functionalized C₁-C₃₀-alkyl, linear    or branched, optionally functionalized C₂-C₃₀-alkenyl, linear or    branched, optionally functionalized C₂-C₃₀-alkynyl, optionally    functionalized C₃-C₂₀-cycloalkyl, optionally functionalized    C₃-C₂₀-cycloalkenyl, optionally functionalized C₁-C₂₀-heteroalkyl,    optionally functionalized C₅-C₂₂-aryl, optionally functionalized    C₆-C₂₃-alkylaryl, optionally functionalized C₆-C₂₃-arylalkyl,    optionally functionalized C₅-C₂₂-heteroaryl, or a unit of the    general formula

Si(R¹¹)_(c)(OR¹²)_(d)],

-   the radicals R¹⁶ are each, independently of one another, hydrogen,    linear or branched, optionally functionalized C₁-C₃₀-alkyl, linear    or branched, optionally functionalized C₂-C₃₀-alkenyl, linear or    branched, optionally functionalized C₂-C₃₀-alkynyl, optionally    functionalized C₃-C₂₀-cycloalkyl, optionally functionalized    C₃-C₂₀-cycloalkenyl, optionally functionalized C₁-C₂₀-heteroalkyl,    optionally functionalized C₅-C₂₂-aryl, optionally functionalized    C₆-C₂₃-alkylaryl, optionally functionalized C₆-C₂₃-arylalkyl,    optionally functionalized C₅-C₂₂-heteroaryl, or a unit of the    general formula

Si(R¹³)_(e)(OR¹⁴)_(f)],

-   R¹¹, R¹²,-   R¹³, R¹⁴,-   R¹⁷, R¹⁸ are each, independently of one another, hydrogen, linear or    branched, optionally functionalized C₁-C₃₀-alkyl, linear or    branched, optionally functionalized C₂-C₃₀-alkenyl, linear or    branched, optionally functionalized C₂-C₃₀-alkynyl, optionally    functionalized C₃-C₂₀-cycloalkyl, optionally functionalized    C₃-C₂₀-cycloalkenyl, optionally functionalized C₁-C₂₀-heteroalkyl,    optionally functionalized C₅-C₂₂-aryl, optionally functionalized    C₆-C₂₃-alkylaryl, optionally functionalized C₆-C₂₃-arylalkyl,    optionally functionalized C₅-C₂₂-heteroaryl,-   n is 1, 2 or 3,-   a, c, e are each, independently of one another, 0, 1 or 2,    preferably 0,-   b is 3-a,-   d is 3-c,-   f is 3-e and-   m, o, p are each, independently of one another, from 1 to 500,    preferably from 1 to 50, particularly preferably from 1 to 20,    and at least one solvent, at least one surface-active substance or a    mixture thereof.

According to the present invention polysiloxanes according to generalformula (II) are polysiloxanes comprising units of general formula (II).The bonding is therein conducted via the *marked bonding respectivelyvia a valid bonding at the Si-atom.

The present invention further relates to a stable mixture comprisingsurface-modified particles which are obtained by reacting metal oxide orsemi-metal oxide particles with at least one compound of general formula(I)

R¹ _(n)—Si(OR²)_(4-n)  (I)

wherein R¹, R² and n have the following meanings:

-   R¹ independently of one another, hydrogen, linear or branched,    optionally functionalized C₁-C₃₀-alkyl, linear or branched,    optionally functionalized C₂-C₃₀-alkenyl, linear or branched,    optionally functionalized C₂-C₃₀-alkynyl, optionally functionalized    C₃-C₂₀-cycloalkyl, optionally functionalized C₃-C₂₀-cycloalkenyl,    optionally functionalized C₁-C₂₀-heteroalkyl, optionally    functionalized C₅-C₂₂-aryl, optionally functionalized    C₆-C₂₃-alkylaryl, optionally functionalized C₆-C₂₃-arylalkyl,    optionally functionalized C₅-C₂₂-heteroaryl,-   R² independently of one another, hydrogen, linear or branched,    optionally functionalized C₁-C₃₀-alkyl, linear or branched,    optionally functionalized C₂-C₃₀-alkenyl, linear or branched,    optionally functionalized C₂-C₃₀-alkynyl, optionally functionalized    C₃-C₂₀-cycloalkyl, optionally functionalized C₃-C₂₀-cycloalkenyl,    optionally functionalized C₁-C₂₀-heteroalkyl, optionally    functionalized C₅-C₂₂-aryl, optionally functionalized    C₆-C₂₃-alkylaryl, optionally functionalized C₆-C₂₃-arylalkyl,    optionally functionalized C₅-C₂₂-heteroaryl,    and/or    -   group of general formula (IIa)

—SiR¹ _(m)(OR²)_(3-m)  (IIa)

wherein R¹ and R² independently of one another have the above-mentionedmeanings and m is independently of one another 0, 1, 2 or 3

-   n 1, 2 or 3    and at least one solvent, at least one surface active substance or a    mixture thereof.

If R² in the compound of general formula (I) has several times, forexample more than once, the meaning of a group of general formula (IIa),corresponding compounds are present, comprising 2, 3, 4 or more unitswith Si-atoms. According to this, in the case, that in general formula(I) R² is several times a group of general formula (IIa), polysiloxanesare present, corresponding to general formula (II).

Furthermore, the object is achieved by the use of the surface-modifiedparticle according to the invention in systems in which the modifiedparticles are brought into contact with at least one solvent, where themass ratio of solvent to modified particle is greater than 500.

The object of the invention is also achieved by the use ofsurface-modified particles according to the invention inagglomeration-deagglomeration cycles.

The stable mixture of the invention comprises surface-modified particleswhich are obtained by reacting metal oxide or semimetal oxide particleswith at least one compound of the general formula (I), a polysiloxane ofthe general formula (II), or a compound of general formula (I)comprising groups of general formula (IIa), which preferably definepolysiloxanes, too.

For the purposes of the present invention, it is generally possible touse all metal oxide or semimetal oxide particles, in particular metaloxide particles, known to those skilled in the art. Examples of metaloxides which are particularly suitable for the purposes of the inventionare the oxides of the metals of the main groups and transition groups ofthe Periodic Table of the Elements, in particular the transition groupsof the Periodic Table of the Elements.

According to the invention, silicon oxide is not preferred as semimetaloxide and is therefore not comprised in a preferred embodiment of thepresent invention.

In a preferred embodiment, the present invention therefore provides themixture according to the invention, with silicon dioxide being exceptedas semimetal oxide.

Examples of suitable metals of the main groups of the Periodic Table ofthe Elements are the alkali metals, for example Li, Na, K, Rb, Cs,alkaline earth metals, for example Be, Mg, Ca, Ba, Sr, the third maingroup of the Periodic Table of the Elements, for example Al, Ga, In, Tl,the fourth main group of the Periodic Table of the Elements, for exampleSn, Pb, or the fifth main group of the Periodic Table of the Elements,for example Sb, Bi.

Examples of suitable metals of the transition groups of the PeriodicTable of the Elements are Sc, Y, the lanthanides, the actinides, Ti, Zr,Hf, Mn, Re, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn and Cd.

In a preferred embodiment, the metal oxide used according to theinvention is an oxide of the metals selected from the group consistingof Li, Na, K, Rb, Cs, Be, Mg, Ca, Ba, Sr, Al, Ga, In, Tl, Sn, Pb, Sb,Bi, Sc, Y, the lanthanides, the actinides, Ti, Zr, Hf, Mn, Re, Fe, Ru,Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd and mixtures thereof,very particularly preferably selected from the group consisting of Mn,Fe, Co, Ni, Cu and combinations thereof. Furthermore, mixed oxides ofthese metals, in particular Mn, Fe, Co, Ni or Cu, with at least onealkaline earth metal, for example Mg, Ca, Sr and/or Ba, are alsosuitable for the purposes of the invention.

The present invention therefore preferably provides the mixture of theinvention in which the metal oxide used is an oxide of a metal selectedfrom the group consisting of Mn, Fe, Co, Ni, Cu, combinations thereofand mixed oxides of these metals with at least one alkaline earth metal,for example Mg, Ca, Sr and/or Ba.

In a particularly preferred embodiment, the present invention providesthe mixture of the invention in which the metal oxide or semimetal oxideparticles are magnetic.

Very particularly preferably preferred metal oxides are iron oxides, forexample Fe₂O₃, magnetic iron oxides, for example magnetite, maghemite,hematite, cubic ferrites of the general formula (III)

M²⁺ _(x)Fe²⁺ _(1-x)Fe³⁺ ₂O₄  (III)

where

-   M is selected from among Co, Ni, Mn, Zn and mixtures thereof and-   x is ≦1,    hexagonal ferrites, for example calcium, barium or strontium ferrite    MFe₆O₁₉ where M=Ca, Sr, Ba, and combinations thereof.

In a preferred embodiment, the metal oxide used according to theinvention is a magnetic iron oxide selected from the abovementionedgroup. In a very particularly preferred embodiment, the at least onemetal oxide used according to the invention is magnetite. Magnetite hasthe formula Fe₃O₄, in particular Fe^(II)Fe^(III) ₂O₄, and is known tothose skilled in the art. Magnetite can be prepared by known processesand is commercially available.

The metal oxide particles used according to the invention can optionallycomprise dopants, for example further metals in oxidic or elementalform, for example noble metals such as platinum.

The particles which are present according to the invention generallyhave a particle size of from 50 nm to 500 μm, preferably from 200 nm to100 μm, particularly preferably from 500 nm to 10 μm.

The particles which are present according to the invention can generallyhave any shape, for example spherical, cylindrical, acicular orcuboidal.

Surface-modified particles which are obtained by reacting metal oxide orsemimetal oxide particles with at least one compound of the generalformula (I)

R¹ _(n)—Si(OR²)_(4-n)  (I)

or polysiloxanes of the general formula (II)

where R¹, R², R³, R⁴, R⁹, R¹⁰, a, b, m and n have the abovementionedmeaning, are present in the stable mixture of the invention.

Preference is given to the radicals R¹ each being, independently of oneanother, linear or branched, optionally functionalized C₁-C₃₀-alkyl,particularly preferably C₁-C₂₀-alkyl, very particularly preferablyC₄-C₁₂-alkyl. In a preferred embodiment, R¹ is linear or branched,unfunctionalized C₁-C₃₀-alkyl, particularly preferably C₁-C₂₀-alkyl,very particularly preferably C₄-C₁₂-alkyl. Examples of linear orbranched C₄-C₁₂-alkyl radicals are butyl, in particular, n-butyl,isobutyl, tert-butyl, pentyl, in particular n-pentyl, isopentyl,tert-pentyl, hexyl, in particular n-hexyl, isohexyl, tert-hexyl, heptyl,in particular n-heptyl, isoheptyl, tert-heptyl, octyl, in particularn-octyl, isooctyl, tert-octyl, nonyl, in particular n-nonyl, isononyl,tert-nonyl, decyl, in particular n-decyl, isodecyl, tert-decyl, undecyl,in particular n-undecyl, isoundecyl, tert-undecyl, or dodecyl, inparticular n-dodecyl, isododecyl, tert-dodecyl.

Further preference is given to the radicals R¹ each being, independentlyof one another, linear or branched, optionally functionalizedC₂-C₃₀-alkenyl, particularly preferably C₂-C₂₀-alkenyl, veryparticularly preferably C₄-C₁₂-alkenyl. Examples of alkenyl radicalswhich are particularly preferred according to the invention are ethenyl(vinyl), propenyl, in particular n-propenyl, isopropenyl, butenyl, inparticular n-butenyl, isobutenyl, tert-butenyl, pentenyl, in particularn-pentenyl, isopentenyl, tert-pentenyl, hexenyl, in particularn-hexenyl, isohexenyl, tert-hexenyl, heptenyl, in particular n-heptenyl,isoheptenyl, tert-heptenyl, octenyl, in particular n-octenyl,isooctenyl, tert-octenyl, nonenyl, in particular n-nonenyl, isononenyl,tert-nonenyl, decenyl, in particular n-decenyl, isodecenyl,tert-decenyl, undecenyl, in particular n-undecenyl, isoundecenyl,tert-undecenyl, or dodecenyl, in particular n-dodecenyl, isododecenyl,tert-dodecenyl.

Further preference is given to the radicals R¹ each being, independentlyof one another, linear or branched, optionally functionalizedC₂-C₃₀-alkynyl, particularly preferably C₂-C₂₀-alkynyl, veryparticularly preferably C₄-C₁₂-alkynyl. Examples of alkynyl radicalswhich are particularly preferred according to the invention are ethynyl,propynyl, in particular n-propynyl, isopropynyl, butynyl, in particularn-butynyl, isobutynyl, tert-butynyl, pentynyl, in particular n-pentynyl,isopentynyl, tert-pentynyl, hexynyl, in particular n-hexynyl,isohexynyl, tert-hexynyl, heptynyl, in particular n-heptynyl,isoheptynyl, tert-heptynyl, octynyl, in particular n-octynyl,isooctynyl, tert-octynyl, nonynyl, in particular n-nonynyl, isononynyl,tert-nonynyl, decynyl, in particular n-decynyl, isodecynyl,tert-decynyl, undecynyl, in particular n-undecynyl, isoundecynyl,tert-undecynyl, or dodecynyl, in particular n-dodecynyl, isododecynyl,tert-dodecynyl.

Further preference is given to the radicals R¹ each being, independentlyof one another, optionally functionalized C₃-C₂₀-cycloalkyl,particularly preferably C₃-C₁₂-cycloalkyl, very particularly preferablyC₃-C₆-cycloalkyl, for example cyclopropyl, cyclobutyl, cyclopentyl,cyclohexyl.

Further preference is given to the radicals R¹ each being, independentlyof one another, optionally functionalized C₃-C₂₀-cycloalkenyl,particularly preferably C₃-C₁₂-cycloalkenyl, very particularlypreferably C₃-C₆-cycloalkenyl, for example cyclopropenyl, cyclobutenyl,cyclopentenyl, cyclohexenyl.

Further preference is given to the radicals R¹ each being, independentlyof one another, optionally functionalized C₁-C₂₀-heteroalkyl,particularly preferably C₁-C₁₂-heteroalkyl. The heteroalkyl radicalspresent according to the invention are derived from the abovementionedalkyl radicals, with at least one carbon atom being replaced by aheteroatom selected from among N, O, P and S.

Further preference is given to the radicals R¹ each being, independentlyof one another, optionally functionalized C₅-C₂₂-aryl, particularlypreferably C₅-C₁₂-aryl. Examples of aryl radicals which are preferredaccording to the invention are phenyl, naphthyl or biaryls.

Further preference is given to the radicals R¹ each being, independentlyof one another, optionally functionalized C₆-C₂₃-alkylaryl, particularlypreferably C₆-C₁₃-alkylaryl. An example of an alklaryl radical which ispreferred according to the invention is benzyl.

Further preference is given to the radicals R¹ each being, independentlyof one another, optionally functionalized C₆-C₂₃-arylalkyl, particularlypreferably C₆-C₁₃-arylalkyl. Examples of arylalkyl radicals which arepreferred according to the invention are tolyl, xylyl, propylbenzyl,hexylbenzyl.

Further preference is given to the radicals R¹ each being, independentlyof one another, optionally functionalized C₅-C₂₂-heteroaryl,particularly preferably C₆-C₁₂-heteroaryl.

The abovementioned radicals R¹ can optionally be functionalized.Suitable functional groups are, for example, selected from among amino,amido, imido, hydroxyl, ether, aldehyde, keto, carboxylic acid, thiol,thioether, hydroxamate and carbamate groups. The abovementioned radicalsR¹ can be singly or multiply functionalized. In the case of multiplefunctionalization, one functional group can be present a plurality oftimes or various functional groups are simultaneously present. Theradicals mentioned for R¹ can also be monosubstituted or polysubstitutedby the abovementioned alkyl, alkenyl, alkynyl, aryl, alkylaryl,arylalkyl, heteroalkyl or heteroaryl radicals.

Very particularly preferred radicals R¹ are octyl, in particularn-octyl, hexyl, in particular n-hexyl and/or butyl, in particularn-butyl, decyl, in particular n-decyl, or dodecyl, in particularn-dodecyl.

For the purposes of the present invention, “independently of oneanother” means that if a plurality of radicals R¹ are present in thecompound of the general formula (I), these can be identical ordifferent.

Preference is given to the radicals R² each being, independently of oneanother, linear or branched, optionally functionalized C₁-C₃₀-alkyl,particularly preferably C₁-C₂₀-alkyl, very particularly preferablyC₁-C₁₂-alkyl. In a preferred embodiment, R² is linear or branched,unfunctionalized C₁-C₃₀-alkyl, particularly preferably C₁-C₂₀-alkyl,very particularly preferably C₁-C₁₂-alkyl. Examples of linear orbranched C₁-C₁₂-alkyl radicals are methyl, ethyl, propyl, in particularn-propyl, isopropyl, butyl, in particular n-butyl, isobutyl, tert-butyl,pentyl, in particular n-pentyl, isopentyl, tert-pentyl, hexyl, inparticular n-hexyl, isohexyl, tert-hexyl, heptyl, in particularn-heptyl, isoheptyl, tert-heptyl, octyl, in particular n-octyl,isooctyl, tert-octyl, nonyl, in particular n-nonyl, isononyl,tert-nonyl, decyl, in particular n-decyl, isodecyl, tert-decyl, undecyl,in particular n-undecyl, isoundecyl, tert-undecyl, or dodecyl, inparticular n-dodecyl, isododecyl, tert-dodecyl.

Further preference is given to the radicals R² each being, independentlyof one another, linear or branched, optionally functionalizedC₂-C₃₀-alkenyl, particularly preferably C₂-C₂₀-alkenyl, veryparticularly preferably C₂-C₁₂-alkenyl. Examples of alkynyl radicalswhich are particularly preferred according to the invention are ethenyl(vinyl), propenyl, in particular n-propenyl, isopropenyl, butenyl, inparticular n-butenyl, isobutenyl, tert-butenyl, pentenyl, in particularn-pentenyl, isopentenyl, tert-pentenyl, hexenyl, in particularn-hexenyl, isohexenyl, tert-hexenyl, heptenyl, in particular n-heptenyl,isoheptenyl, tert-heptenyl, octenyl, in particular n-octenyl,isooctenyl, tert-octenyl, nonenyl, in particular n-nonenyl, isononenyl,tert-nonenyl, decenyl, in particular n-decenyl, isodecenyl,tert-decenyl, undecenyl, in particular n-undecenyl, isoundecenyl,tert-undecenyl, or dodecenyl, in particular n-dodecenyl, isododecenyl,tert-dodecenyl.

Further preference is given to the radicals R² each being, independentlyof one another, linear or branched, optionally functionalizedC₂-C₃₀-alkynyl, particularly preferably C₂-C₂₀-alkynyl, veryparticularly preferably C₂-C₁₂-alkynyl. Examples of alkynyl radicalswhich are particularly preferred according to the invention are ethynyl,propynyl, in particular n-propynyl, isopropynyl, butynyl, in particularn-butynyl, isobutynyl, tert-butynyl, pentynyl, in particular n-pentynyl,isopentynyl, tert-pentynyl, hexynyl, in particular n-hexynyl,isohexynyl, tert-hexynyl, heptynyl, in particular n-heptynyl,isoheptynyl, tert-heptynyl, octynyl, in particular n-octynyl,isooctynyl, tert-octynyl, nonynyl, in particular n-nonynyl, isononynyl,tert-nonynyl, decynyl, in particular n-decynyl, isodecynyl,tert-decynyl, undecynyl, in particular n-undecynyl, isoundecynyl,tert-undecynyl, or dodecynyl, in particular n-dodecynyl, isododecynyl,tert-dodecynyl.

Further preference is given to the radicals R² each being, independentlyof one another, optionally functionalized C₃-C₂₀-cycloalkyl,particularly preferably C₃-C₁₂-cycloalkyl, particularly preferablyC₃-C₆-cycloalkyl, for example cyclopropyl, cyclobutyl, cyclopentyl,cyclohexyl.

Further preference is given to the radicals R² each being, independentlyof one another, optionally functionalized C₃-C₂₀-cycloalkenyl,particularly preferably C₃-C₁₂-cycloalkenyl, very particularlypreferably C₃-C₆-cycloalkenyl, for example cyclopropenyl, cyclobutenyl,cyclopentenyl, cyclohexenyl.

Further preference is given to the radicals R² each being, independentlyof one another, optionally functionalized C₁-C₂₀-heteroalkyl,particularly preferably C₄-C₁₂-heteroalkyl. The heteroalkyl radicalswhich are present according to the invention are derived from theabovementioned alkyl radicals, with at least one carbon atom beingreplaced by a heteroatom selected from among N, O, P and S.

Further preference is given to the radicals R² each being, independentlyof one another, optionally functionalized C₅-C₂₂-aryl, particularlypreferably C₅-C₁₂-aryl. Examples of aryl radicals which are preferredaccording to the invention are phenyl, naphthyl or biaryls.

Further preference is given to the radicals R² each being, independentlyof one another, optionally functionalized C₆-C₂₃-alkylaryl, particularlypreferably C₆-C₁₃-alkylaryl. An example of an alkylaryl radical which ispreferred according to the invention is benzyl.

Further preference is given to the radicals R² each being, independentlyof one another, optionally functionalized C₆-C₂₃-arylalkyl, particularlypreferably C₆-C₁₃-arylalkyl. Examples of arylalkyl radicals which arepreferred according to the invention are tolyl, xylyl, propylbenzyl,hexylbenzyl.

Further preference is given to the radicals R² each being, independentlyof one another, optionally functionalized C₅-C₂₂-heteroaryl,particularly preferably C₅-C₁₂-heteroaryl.

The abovementioned radicals R² can optionally be functionalized.Suitable functional groups are, for example, selected from among amino,amido, imido, hydroxy, ether, aldehyde, keto, carboxylic acid, thiol,thioether, hydroxamate and carbamate groups. The abovementioned radicalsR¹ can be singly or multiply functionalized. In the case of multiplefunctionalization, one functional group can be present a plurality oftimes or various functional groups are simultaneously present. Theradicals mentioned for R² can also be monosubstituted or polysubstitutedby the abovementioned alkyl, alkenyl, alkynyl, aryl, alkylaryl,arylalkyl, heteroalkyl or heteroaryl radicals.

Very particularly preferred radicals R² are methyl and/or ethyl.

The present invention therefore preferably provides the mixture of theinvention in which R² in the compound of the general formula (I) ismethyl or ethyl.

In a further preferred embodiment R² is a group of general formula (IIa)

—SiR¹ _(m)(OR²)_(3-n)  (IIa)

wherein R¹ and R² independently of one another have the above-mentionedmeanings and m is independently of one another 0, 1, 2 or 3, preferably1 or 2. The connection of this group of general formula (IIa) to thecompound of general formula (I) is via the free bonding at the Si-atom.

In a preferred embodiment R¹ in the group of general formula (IIa) isindependently of one another octyl, preferably n-octyl, hexyl,preferably n-hexyl and/or -butyl, preferably n-butyl, decyl, preferablyn-decyl or docecyl, preferably n-dodecyl.

In a particularly preferred embodiment R² is in the group of generalformula (IIa) independently of one another methyl or ethyl.

Therefore, the present invention preferably relates to the mixtureaccording to the present invention, wherein in the compound of generalformula (I) or in the group of general formula (IIa) R² is methyl orethyl.

If in the compound of general formula (I) groups of general formula(IIa) are present several times, according to the present inventionpolysiloxanes are used as compounds of general formula (I). If accordingto the present invention polysiloxanes comprising groups of generalformula (IIa) are used, these can be linear or branched. Polysiloxaneswhich are used according to the present invention comprising groups ofthe general formula (IIa) have in general a molecular weight of 250 to200,000 g/mol, preferably 250 to 20,000 g/mol, particularly preferably300 to 5,000 g/mol.

For the purposes of the present invention, “independently of oneanother” means that if a plurality of radicals R² are present in thecompound of the general formula (I), these can be identical ordifferent.

Preference is given to the radicals R³ each being, independently of oneanother, linear or branched, optionally functionalized C₁-C₃₀-alkyl,particularly preferably C₁-C₂₀-alkyl, very particularly preferablyC₁-C₁₂-alkyl. In a preferred embodiment, R³ is linear or branched,unfunctionalized C₁-C₃₀-alkyl, particularly preferably C₁-C₂₀-alkyl,very particularly preferably C₁-C₁₂-alkyl. Examples of linear orbranched C₁-C₁₂-alkyl radicals are methyl, ethyl, propyl, in particularn-propyl, isopropyl, butyl, in particular n-butyl, isobutyl, tert-butyl,pentyl, in particular n-pentyl, isopentyl, tert-pentyl, hexyl, inparticular n-hexyl, isohexyl, tert-hexyl, heptyl, in particularn-heptyl, isoheptyl, tert-heptyl, octyl, in particular n-octyl,isooctyl, tert-octyl, nonyl, in particular n-nonyl, isononyl,tert-nonyl, decyl, in particular n-decyl, isodecyl, tert-decyl, undecyl,in particular n-undecyl, isoundecyl, tert-undecyl, or dodecyl, inparticular n-dodecyl, isododecyl, tert-dodecyl.

Further preference is given to the radicals R³ each being, independentlyof one another, linear or branched, optionally functionalizedC₂-C₃₀-alkenyl, particularly preferably C₂-C₂₀-alkenyl, veryparticularly preferably C₂-C₁₂-alkenyl. Examples of alkenyl radicalswhich are particularly preferred according to the invention are ethenyl(vinyl), propenyl, in particular n-propenyl, isopropenyl, butenyl, inparticular n-butenyl, isobutenyl, tert-butenyl, pentenyl, in particularn-pentenyl, isopentenyl, tert-pentenyl, hexenyl, in particularn-hexenyl, isohexenyl, tert-hexenyl, heptenyl, in particular n-heptenyl,isoheptenyl, tert-heptenyl, octenyl, in particular n-octenyl,isooctenyl, tert-octenyl, nonenyl, in particular n-nonenyl, isononenyl,tert-nonenyl, decenyl, in particular n-decenyl, isodecenyl,tert-decenyl, undecenyl, in particular n-undecenyl, isoundecenyl,tert-undecenyl, or dodecenyl, in particular n-dodecenyl, isododecenyl,tert-dodecenyl.

Further preference is given to the radicals R³ each being, independentlyof one another, linear or branched, optionally functionalizedC₂-C₃₀-alkynyl, particularly preferably C₂-C₂₀-alkynyl, veryparticularly preferably C₂-C₁₂-alkynyl. Examples of alkynyl radicalswhich are particularly preferred according to the invention are ethynyl,propynyl, in particular n-propynyl, isopropynyl, butynyl, in particularn-butynyl, isobutynyl, tert-butynyl, pentynyl, in particular n-pentynyl,isopentynyl, tert-pentynyl, hexynyl, in particular n-hexynyl,isohexynyl, tert-hexynyl, heptynyl, in particular n-heptynyl,isoheptynyl, tert-heptynyl, octynyl, in particular n-octynyl,isooctynyl, tert-octynyl, nonynyl, in particular n-nonynyl, isononynyl,tert-nonynyl, decynyl, in particular n-decynyl, isodecynyl,tert-decynyl, undecynyl, in particular n-undecynyl, isoundecynyl,tert-undecynyl, or dodecenyl, in particular n-dodecynyl, isododecynyl,tert-dodecynyl.

Further preference is given to the radicals R³ each being, independentlyof one another, optionally functionalized C₃-C₂₀-cycloalkyl,particularly preferably C₃-C₁₂-cycloalkyl, particularly preferablyC₃-C₆-cycloalkyl, for example cyclopropyl, cyclobutyl, cyclopentyl,cyclohexyl.

Further preference is given to the radicals R³ each being, independentlyof one another, optionally functionalized C₃-C₂₀-cycloalkenyl,particularly preferably C₃-C₁₂-cycloalkenyl, very particularlypreferably C₃-C₆-cycloalkenyl, for example cyclopropenyl, cyclobutenyl,cyclopentenyl, cyclohexenyl.

Further preference is given to the radicals R³ each being, independentlyof one another, optionally functionalized C₁-C₂₀-heteroalkyl,particularly preferably C₁-C₁₂-heteroalkyl. The heteroalkyl radicalswhich are present according to the invention are derived from theabovementioned alkyl radicals, with at least one carbon atom beingreplaced by a heteroatom selected from among N, O, P and S.

Further preference is given to the radicals R³ each being, independentlyof one another, optionally functionalized C₅-C₂₂-aryl, particularlypreferably C₅-C₁₂-aryl. Examples of aryl radicals which are preferredaccording to the invention are phenyl, naphthyl, biaryls.

Further preference is given to the radicals R³ each being, independentlyof one another, optionally functionalized C₆-C₂₃-alkylaryl, particularlypreferably C₆-C₁₃-alkylaryl. An example of an alkylaryl radical which ispreferred according to the invention is benzyl.

Further preference is given to the radicals R³ each being, independentlyof one another, optionally functionalized C₆-C₂₃-arylalkyl, particularlypreferably C₆-C₁₃-arylalkyl. Examples of arylalkyl radicals which arepreferred according to the invention are tolyl, xylyl, propylbenzyl,hexylbenzyl.

Further preference is given to the radicals R³ each being, independentlyof one another, optionally functionalized C₅-C₂₂-heteroaryl,particularly preferably C₅-C₁₂-heteroaryl.

R³ can, in one embodiment, be —OR¹⁷, where R¹⁷ has the abovementionedmeanings. In one possible embodiment, possible and preferred embodimentsof R¹⁷ correspond, independently of one another, to the possible andpreferred embodiments mentioned for R². In this embodiment, R¹⁷ is veryparticularly preferably selected from among methyl, ethyl, hexyl, octyl,decyl, dodecyl. When R³ is —OR¹⁷, crosslinked siloxane structures areformed in the modification of the particle surface.

In a further preferred embodiment of the present invention, R³ is a unitof the general formula

where R⁵, R⁶, R¹⁵ and o have the above-mentioned meanings.

The preferred embodiments of R⁵ and R⁶ correspond, independently of oneanother, to the possible and preferred embodiments mentioned for R². R⁵and R⁶ are very particularly preferably selected independently fromamong methyl, ethyl, hexyl, octyl, decyl, dodecyl.

In one possible embodiment, possible and preferred embodiments of R¹⁵correspond, independently of one another, to the possible and preferredembodiments mentioned for R². In this embodiment, R¹⁵ is veryparticularly preferably selected from among methyl, ethyl.

In a further embodiment according to the invention, R¹⁵ can be a unit ofthe general formula

Si(R¹¹)_(c)(OR¹²)_(d)],

where R¹¹, R¹², c and d have the above-mentioned meanings.

In one possible embodiment, possible and preferred embodiments of R¹¹correspond, independently of one another, to the possible and preferredembodiments mentioned for R². In this embodiment, R¹¹ is veryparticularly preferably selected from among methyl, ethyl, hexyl, octyl,decyl, dodecyl.

In one possible embodiment, possible and preferred embodiments of R¹²correspond, independently of one another, to the possible and preferredembodiments mentioned for R². In this embodiment, R¹² is veryparticularly preferably selected from among methyl, ethyl.

The indices c are each, independently of one another, 0, 1 or 2,preferably 0.

d is 3-c, i.e. d can assume the values 1, 2, or 3, with 3 beingpreferred.

The abovementioned radicals R³ can optionally be functionalized.Suitable functional groups are, for example, selected from among amino,amido, imido, hydroxy, ether, aldehyde, keto, carboxylic acid, thiol,thioether, hydroxamate and carbamate groups. The abovementioned radicalsR¹ can be singly or multiply functionalized. In the case of multiplefunctionalization, one functional group can be present a plurality oftimes or various functional groups are simultaneously present.Furthermore, the radicals mentioned for R¹ can also be monosubstitutedor polysubstituted by the abovementioned alkyl, alkenyl, alkynyl, aryl,alkylaryl, arylalkyl, heteroalkyl or heteroaryl radicals.

Very particularly preferred radicals R³ are methyl, butyl, in particularn-butyl, hexyl, in particular n-hexyl, octyl, in particular n-octyl,decyl, in particular n-decyl and dodecyl, in particular n-dodecyl.

For the purposes of the present invention, “independently of oneanother” means that if a plurality of radicals R³ are present in thecompound of the general formula (II), these can be identical ordifferent.

Preference is given to the radicals R⁴ each being, independently of oneanother, linear or branched, optionally functionalized C₁-C₃₀-alkyl,particularly preferably C₁-C₂₀-alkyl, very particularly preferablyC₁-C₁₂-alkyl. In a preferred embodiment, R⁴ is linear or branched,unfunctionalized C₁-C₃₀-alkyl, particularly preferably C₁-C₂₀-alkyl,very particularly preferably C₁-C₁₂-alkyl. Examples of linear orbranched C₁-C₁₂-alkyl radicals are methyl, ethyl, propyl, in particularn-propyl, isopropyl, butyl, in particular n-butyl, isobutyl, tert-butyl,pentyl, in particular n-pentyl, isopentyl, tert-pentyl, hexyl, inparticular n-hexyl, isohexyl, tert-hexyl, heptyl, in particularn-heptyl, isoheptyl, tert-heptyl, octyl, in particular n-octyl,isooctyl, tert-octyl, nonyl, in particular n-nonyl, isononyl,tert-nonyl, decyl, in particular n-decyl, isodecyl, tert-decyl, undecyl,in particular n-undecyl, isoundecyl, tert-undecyl, or dodecyl, inparticular n-dodecyl, isododecyl, tert-dodecyl.

Further preference is given to the radicals R⁴ each being, independentlyof one another, linear or branched, optionally functionalizedC₂-C₃₀-alkenyl, particularly preferably C₂-C₂₀-alkenyl, veryparticularly preferably C₂-C₁₂-alkenyl. Examples of alkenyl radicalswhich are particularly preferred according to the invention are ethenyl(vinyl), propenyl, in particular n-propenyl, isopropenyl, butenyl, inparticular n-butenyl, isobutenyl, tert-butenyl, pentenyl, in particularn-pentenyl, isopentenyl, tert-pentenyl, hexenyl, in particularn-hexenyl, isohexenyl, tert-hexenyl, heptenyl, in particular n-heptenyl,isoheptenyl, tert-heptenyl, octenyl, in particular n-octenyl,isooctenyl, tert-octenyl, nonenyl, in particular n-nonenyl, isononenyl,tert-nonenyl, decenyl, in particular n-decenyl, isodecenyl,tert-decenyl, undecenyl, in particular n-undecenyl, isoundecenyl,tert-undecenyl, or dodecenyl, in particular n-dodecenyl, isododecenyl,tert-dodecenyl.

Further preference is given to the radicals R⁴ each being, independentlyof one another, linear or branched, optionally functionalizedC₂-C₃₀-alkynyl, particularly preferably C₂-C₂₀-alkynyl, veryparticularly preferably C₂-C₁₂-alkynyl. Examples of alkynyl radicalswhich are particularly preferred according to the invention are ethynyl,propynyl, in particular n-propynyl, isopropynyl, butynyl, in particularn-butynyl, isobutynyl, tert-butynyl, pentynyl, in particular n-pentynyl,isopentynyl, tert-pentynyl, hexynyl, in particular n-hexynyl,isohexynyl, tert-hexynyl, heptynyl, in particular n-heptynyl,isoheptynyl, tert-heptynyl, octynyl, in particular n-octynyl,isooctynyl, tert-octynyl, nonynyl, in particular n-nonynyl, isononynyl,tert-nonyl, decynyl, in particular n-decynyl, isodecynyl, tert-decynyl,undecynyl, in particular n-undecynyl, isoundecynyl, tert-undecynyl, ordodecenyl, in particular n-dodecynyl, isododecynyl, tert-dodecynyl.

Further preference is given to the radicals R⁴ each being, independentlyof one another, optionally functionalized C₃-C₂₀-cycloalkyl,particularly preferably C₃-C₁₂-cycloalkyl, particularly preferablyC₃-C₆-cycloalkyl, for example cyclopropyl, cyclobutyl, cyclopentyl,cyclohexyl.

Further preference is given to the radicals R⁴ each being, independentlyof one another, optionally functionalized C₃-C₂₀-cycloalkenyl,particularly preferably C₃-C₁₂-cycloalkenyl, very particularlypreferably C₃-C₆-cycloalkenyl, for example cyclopropenyl, cyclobutenyl,cyclopentenyl, cyclohexenyl.

Further preference is given to the radicals R⁴ each being, independentlyof one another, optionally functionalized C₁-C₂₀-heteroalkyl,particularly preferably C₁-C₁₂-heteroalkyl. The heteroalkyl radicalswhich are present according to the invention are derived from theabovementioned alkyl radicals, with at least one carbon atom beingreplaced by a heteroatom selected from among N, O, P and S.

Further preference is given to the radicals R⁴ each being, independentlyof one another, optionally functionalized C₅-C₂₂-aryl, particularlypreferably C₅-C₁₂-aryl. Examples of aryl radicals which are preferredaccording to the invention are phenyl, naphthyl, biaryls.

Further preference is given to the radicals R⁴ each being, independentlyof one another, optionally functionalized C₆-C₂₃-alkylaryl, particularlypreferably C₆-C₁₃-alkylaryl. An example of an alkylaryl radical which ispreferred according to the invention is benzyl.

Further preference is given to the radicals R⁴ each being, independentlyof one another, optionally functionalized C₆-C₂₃-arylalkyl, particularlypreferably C₆-C₁₃-arylalkyl. Examples of arylalkyl radicals which arepreferred according to the invention are tolyl, xylyl, propylbenzyl,hexylbenzyl.

Further preference is given to the radicals R⁴ each being, independentlyof one another, optionally functionalized C₅-C₂₂-heteroaryl,particularly preferably C₅-C₁₂-heteroaryl.

R⁴ can, in one embodiment, be —OR¹⁸, where R¹⁸ has the abovementionedmeanings. In one possible embodiment, possible and preferred embodimentsof R¹⁸ correspond, independently of one another, to the possible andpreferred embodiments mentioned for R². In this embodiment, R¹⁸ is veryparticularly preferably selected from among methyl, ethyl, hexyl, octyl,decyl, dodecyl. When R⁴ is —OR¹⁸, crosslinked siloxane structures areformed in the modification of the particle surface.

In a further preferred embodiment of the present invention, R⁴ is a unitof the general formula

where R⁷, R⁸, R¹⁶ and p have the above-mentioned meanings.

The preferred embodiments of R⁷ and R⁸ correspond, independently of oneanother, to the possible and preferred embodiments mentioned for R². R⁷and R⁸ are very particularly preferably selected independently fromamong methyl, ethyl, hexyl, octyl, decyl, dodecyl.

In one possible embodiment, possible and preferred embodiments of R¹⁶correspond, independently of one another, to the possible and preferredembodiments mentioned for R². In this embodiment, R¹⁶ is veryparticularly preferably selected from among methyl, ethyl.

In a further embodiment of the invention, R¹⁶ can be a unit of thegeneral formula

Si(R¹³)_(e)(OR¹⁴)_(f)],

where R¹³, R¹⁴, e and f have the abovementioned meanings.

In one possible embodiment, possible and preferred embodiments of R¹³correspond, independently of one another, to the possible and preferredembodiments mentioned for R². In this embodiment, R¹³ is veryparticularly preferably selected from among methyl, ethyl, hexyl, octyl,decyl, dodecyl.

In one possible embodiment, possible and preferred embodiments of R¹⁴correspond, independently of one another, to the possible and preferredembodiments mentioned for R². In this embodiment, R¹⁴ is veryparticularly preferably selected from among methyl, ethyl.

The indices e are each, independently of one another, 0, 1 or 2,preferably 0.

f is 3-e, i.e. f can assume the values 1, 2 or 3, with 3 beingpreferred.

The abovementioned radicals R⁴ can optionally be functionalized.Suitable functional groups are, for example, selected from among amino,amido, imido, hydroxy, ether, aldehyde, keto, carboxylic acid, thiol,thioether, hydroxamate and carbamate groups. The abovementioned radicalsR¹ can be simply or multiply functionalized. In the case of multiplefunctionalization, one functional group can be present a plurality oftimes or various functional groups are simultaneously present.Furthermore, the radicals mentioned for R¹ can also be monosubstitutedor polysubstituted by the abovementioned alkyl, alkenyl, alkynyl, aryl,alkylaryl, arylalkyl, heteroalkyl or heteroaryl radicals.

Very particularly preferred radicals R⁴ are methyl and ethyl.

For the purposes of the present invention, “independently of oneanother” means that if a plurality of radicals R⁴ are present in thecompound of the general formula (II), these can be identical ordifferent.

What has been said in respect of the radicals R³ and R⁴ applies,independently, to the radicals R⁵, R⁶, R⁷ and R⁸. Particularly preferredradicals R⁵, R⁶, R⁷ and R⁸ are selected independently from among methyland ethyl.

In the compound of the general formula (I), n is generally 1, 2 or 3. nin the compound of the general formula (I) is preferably 1 or 2. n inthe compound of the general formula (I) is particularly preferably 1.

The present invention therefore preferably provides the mixture of theinvention in which n in the compound of the general formula (I) is 1 or2, particularly preferably 1.

In the polysiloxanes of the general formula (II) m, o and p are each,independently of one another, generally from 1 to 500, preferably from 1to 50, particularly preferably from 1 to 20.

Compounds of the general formula (I) which are particularly preferredaccording to the invention are selected from the group consisting of[2-(3-cyclohexenyl)ethyl]trimethoxysilane,trimethoxy(7-octen-1-yl)silane, isooctyltrimethoxy-silane,N-(3-triethoxysilylpropyl)methoxyethoxyethoxyethylcarbamate,N-(3-triethoxy-silylpropyl)methoxyethoxyethoxyethylcarbamate,3-(methacryloyloxy)propyltrimethoxy-silane, allyltrimethoxysilane,3-acryloxypropyltrimethoxysilane,3-(methacryloyloxy)-propyltriethoxysilane,3-(methacryloyloxy)propylmethyldimethoxysilane,3-(acryloyloxy-propyl)methyldimethoxysilane,3-(methacryloyloxy)propyldimethylethoxysilane,3-(methacryloyloxy)propyldimethylethoxysilane,vinyldimethyl-5-ethoxysilane, phenyl-trimethoxysilane,n-octyltrimethoxysilane, dodecyltrimethoxysilane,isooctyltrimethoxy-silane, octadecyltrimethoxysilane,propyltrimethoxysilane, hexyltrimethoxysilane,vinylmethyldiacetoxysilane, vinylmethyldiethoxysilane,vinyltriacetoxysilane, vinyltriethoxysilane, vinyltriisopropoxysilane,vinyltrimethoxysilane, vinyltriphenoxy-silane, vinyltritbutoxysilane,vinyltrisisobutoxysilane, vinyltriisopropenoxysilane,vinyltris(2-methoxyethoxy)silane, styrylethyltrimethoxysilane,mercaptopropyl-trimethoxysilane, 3-glycidoxypropyltrimethoxysilane,heptamethyl(2-[tris(2-methoxyethoxy)silyl]ethyl)trisiloxane and mixturesthereof.

One class of polysiloxanes of the general formula (II) respectivelypolysiloxanes of general formula (I) comprising groups of generalformula (IIa) which is preferred according to the invention ispolydimethylsiloxanes which can have, for example, methoxy and/or ethoxyend groups.

The reaction of the abovementioned metal oxide or semimetal oxideparticles with the compounds of the general formula (I) or thepolysiloxanes of the general formula (II) respectively polysiloxanes ofgeneral formula (I) comprising groups of general formula (IIa) can becarried out by processes known to those skilled in the art, for examplecontacting of the substrates in a solvent, for example toluene or water,at a temperature in the range from room temperature to the boiling pointof the solvent. After conventional work-up, the reaction product ofmetal oxide or semimetal oxide particles and compounds of the generalformula (I) or polysiloxanes of the general formula (II) respectivelypolysiloxanes of general formula (I) comprising groups of generalformula (IIa) can be obtained.

Here, hydrolysis of the silicon ether (Si—OR+H₂O) to the silanol(Si—OH+ROH) occurs in a first step, followed in a second step bycondensation of the surface hydroxyl groups with the silanol to give theproduct (Si—OH+M-OH→Si—O-M+H₂O). According to the invention, only SiOR²can be hydrolyzed in the above-mentioned silicon-comprising compounds;R¹, R³ and all further radicals mentioned cannot be hydrolyzed.

Hydrolysis of alkoxysilanes can be accelerated by decreasing thepH-value of the solution by addition of acids. In one embodiment thisstep can be conducted before the silanes are contacted with the metal-or semi-metal oxide particles, or, in a second embodiment, afterwards.In the later case, pH-value and acid are selected in a way that oxideparticles are not attacked thereby. Preferred is the use of acetic acidor nitric acid. Further preferred is adjustment of the pH-value of 3 to4. Under certain circumstances, the pH-value of the reaction mixturechanges during reaction. In this case, it is useful to adjust thepH-value for completion of surface fixation to 3 to 4, again. A furtheracceleration of the reaction can be achieved by working at increasedtemperature, preferably near the boiling point of the solvent.

After obtaining the desired reaction degree, the solid can be separatedfrom the solution by filtration or similar processes, known to theskilled artisan, or the solution is, preferably, dried under using ofdecreased pressure and/or increased temperature.

If desired, the condensation degree of the hydroxy species and therewiththe cross-linking is increased afterwards, by a temperature treatment.It has to be noted that this temperature should be selected in a waythat all reaction partners are stable under these given conditions. In aparticularly preferred embodiment, temperatures above room temperature,for example up to 200° C., particularly up to 160° C. Water that isformed in the condensation is preferably additionally removed from thereaction zone.

A further possibility to contact the silane reagent with the metal- orsemi-metal oxide particles is by spraying of a solution of the reagentonto the solid. Preferably, alkoxysilanes that are already in solutionare transferred into silanoles. An advantage of this embodiment is, thatless solvent has to be evaporated in the drying step. Treatment afterdrying can be conducted as mentioned above.

The present invention therefore also relates to a process for thepreparation of a surface-modified particle as defined above bycontacting the metal- or semi-metal oxide particle, which is to bemodified with a compound of general formula (I) or with polysiloxanes ofgeneral formula (I), comprising groups of general formula (IIa), asdefined above.

The present invention preferably relates to the process according to thepresent invention, wherein the contacting of the metal- or semi-metaloxide particle that is to be modified with the compound of generalformula (I) or with polysiloxanes of general formula (I), comprisinggroups of general formula (IIa) as defined above, is conducted byspraying.

The present invention preferably relates to the process according to thepresent invention, wherein the reaction is accelerated by adjusting ofthe pH-value, preferably by addition of acid.

The present invention preferably relates to the process according to thepresent invention, wherein a temperature treatment is conducted afterdrying of the products, preferably at up to 160° C.

The present invention preferably relates to the process according to thepresent invention, wherein the contacting is conducted by spraying thecompounds of general formula (I) or the polysiloxanes of general formula(I) comprising groups of general formula (IIa) as defined above, ontothe metal- or semi-metal oxide particle that is to be modified.

The stable mixture of the invention comprises at least one solvent, atleast one surface-active substance or a mixture thereof in addition tothe abovementioned functionalized metal oxide or semimetal oxideparticles.

According to the invention, it has surprisingly been found that thereaction products according to the invention, i.e. thesurface-functionalized metal oxide or semimetal oxide particles, areparticularly stable in mixtures with solvents and/or surface-activecompounds, i.e. no detachment of the silicon compounds bound to thesurface occurs.

The at least one solvent present in the mixture of the invention ispreferably selected from the group consisting of aromatic hydrocarbons,for example benzene, toluene, xylene, alcohols, for example methanol,ethanol, propanols such as n-propanol, isopropanol, butanols such asn-butanol, isobutanol, tert-butanol, ethers such as diethyl ether,methyl tert-butyl ether, isobutyl tert-butyl ether, cyclic ethers suchas tetrahydrofuran, dioxane, esters, cyclic esters, alkanes such ashexane, cycloalkanes such as cyclohexane, olefins, cycloolefins, waterand mixtures thereof. If mixtures of solvents are used according to theinvention, preference is given to using solvents which are completelymiscible with one another, i.e. form a single phase on mixing.

The present invention therefore preferably provides the mixture of theinvention in which the at least one solvent is selected from the groupconsisting of aromatic hydrocarbons, preferably benzene, toluene,xylene, alcohols, for example methanol, ethanol, propanols such asn-propanol, isopropanol, butanols such as n-butanol, isobutanol,tert-butanol, ethers such as diethyl ether, methyl tert-butyl ether,isobutyl-tert-butyl ether, cyclic ethers such as tetrahydrofuran,dioxane, esters, cyclic esters, alkanes such as hexane, cycloalkanessuch as cyclohexane, olefins, cycloolefins, water and mixtures thereof.

In a preferred embodiment, the mixture of the invention is used inprocesses in which the surface-modified particles are brought intocontact with particularly large amounts of solvents.

The mixture of the invention generally has a solids content of up to 70%by weight, preferably up to 60% by weight. The content of at least onesolvent in the mixture of the invention is therefore generally at least30% by weight, preferably at least 40% by weight, i.e. in general from30 to 99.9% by weight, preferably from 40 to 99.9% by weight, ofsolvent. According to the invention, the solids content is the contentof particles which have been modified on the surface according to theinvention and any further solids present.

The at least one surface-active substance present in the mixture of theinvention is preferably selected from the group consisting of nonionic,anionic, cationic or zwitterionic surfactants and mixtures thereof.

Preferred examples of nonionic surfactants are fatty alcohol polyglycolethers, in particular fatty alcohol polyethylene glycol ethers.

Preferred examples of anionic surfactants are alkylbenzenesulfonates,secondary alkanesulfonates, α-olefinsulfonates, fatty alcohol sulfatesor fatty alcohol ether sulfates.

Preferred examples of cationic surfactants are stearyltrimethylammoniumsalts.

Preferred examples of zwitterionic surfactants are sultaines, fatty acidamidoalkylhydroxysultaine or alkyl betaines.

Particularly preferred surface-active substances are sodium alkylphenolether sulfates.

The at least one surface-active substance is generally present in themixture of the invention in an amount of from 0.001 to 20% by weight,preferably from 0.01 to 15% by weight, particularly preferably from 0.1to 10% by weight, in each case based on the total mixture. If at leastone surface-active substance is present according to the invention, theabovementioned amount of at least one solvent is modified accordingly.

The surface-functionalized metal oxide or semimetal oxide particles aregenerally present in the mixture of the invention in an amount of from0.1 to 70% by weight, preferably from 0.1 to 60% by weight.

If further solids are optionally present in the mixture of theinvention, the abovementioned amount of surface-functionalized metaloxide or semimetal oxide particles is modified accordingly.

In all possible embodiments, the amounts of surface-functionalized metaloxide or semimetal oxide particles, at least one solvent, optionallypresent surface-active substances and optionally present further solidsadd up to 100% by weight.

Apart from the functionalized particles, the at least one solvent and/orthe at least one surface-active substance, the mixture of the inventioncan comprise further components, for example oxidic or metallic solidsand further hydrophobic components. The sum of the amounts of thecomponents present in the mixture of the invention in each case add upto 100% by weight.

The mass ratio of solvent to modified particles in the mixture of theinvention is generally greater than 500, preferably 1000, particularlypreferably greater than 5000, very particularly preferably greater than10 000.

For the purposes of the present invention, the term “stable mixture”means that the surface-functionalized metal oxide or semimetal oxideparticles present in the mixture of the invention are not changed in themixture, i.e. the silyl groups present on the surface are not detachedfrom the surface of the metal oxide or semimetal oxide particles, forexample by hydrolysis, so that the mixture of the invention as a wholedoes not change or changes only slightly. That a mixture comprisingsurface-modified particles is stable for the purposes of the presentinvention can be demonstrated, for example, by the fact that suchparticles which are in contact with solvents and/or surface-activesubstance in a mixture according to the invention remain chemicallyand/or physically unchanged. This can, for example, be determined byelemental analysis or determination of the hydrophobic properties, forexample by determination of the ability to float or the contact angle.

The present invention also provides a process for treatingsurface-modified particles according to the invention with at least onesolvent, wherein the mass ratio of solvent to modified particle isgreater than 500.

As regards the surface-modified particles and the solvents, what hasbeen said above in respect of the mixture according to the inventionapplies to the process of the invention.

In the process of the invention, the mass ratio of surface-modifiedparticle and the at least one solvent is generally greater than 500,preferably greater than 1000, particularly preferably greater than 5000,very particularly preferably greater than 10 000.

In this process of the invention, the surface-modified particlesaccording to the invention are brought into contact, i.e. treated, witha relatively large amount of solvent. Corresponding systems according tothe invention in which this treatment can be carried out are, forexample, flowing systems in which the surface-modified particles of theinvention are brought into contact in, for example, continuous processeswith further substances, particles, materials, etc., for examplecontinuous processes for agglomeration with further substances,particles, materials, etc., in solution or dispersion. The process ofthe invention also relates to deagglomeration of agglomerates of thesurface-modified particles of the invention and further substances,particles or materials, or of agglomerates of the surface-modifiedparticles with themselves, for example likewise in flowing systems.

The present invention also provides for the use of surface-modifiedparticles according to the invention in systems in which the modifiedparticles are brought into contact with at least one solvent, whereinthe mass ratio of solvent to modified particles is greater than 500.

As regards the surface-modified particles and the solvents, what hasbeen said above in respect of the mixture of the invention applies.

The mass ratio of surface-modified particle and the at least one solventis generally greater than 500, preferably greater than 1000,particularly preferably greater than 5000, very particularly preferablygreater than 10 000.

In this use according to the invention, the surface-modified particlesof the invention are brought into contact with a relatively large amountof solvent. Corresponding systems according to the invention in whichthis contacting can be carried out are, for example, flowing systems inwhich the surface-modified particles of the invention are brought intocontact in, for example, continuous processes with further substances,particles, materials, etc., for example continuous processes foragglomeration with further substances, particles, materials, etc., insolution or dispersion. The use according to the invention also relatesto deagglomeration of agglomerates of the surface-modified particles ofthe invention and further substances, particles or materials, or ofagglomerates of surface-modified particles with themselves, for examplelikewise in flowing systems.

The present invention also provides for the use of surface-modifiedparticles according to the invention, in particular magnetic particles,in agglomeration-deagglomeration cycles.

In this use too, what has been said in respect of the mixture of theinvention applies to the surface-modified particles and the solvents.

According to the invention, an agglomeration-deagglomeration cycle is aprocess in which the surface-functionalized particles of the invention,in particular magnetic particles, are brought into contact withthemselves or other particles, substances, materials, etc., in solutionor dispersion and agglomerate as a result of hydrophobic interaction,ionic forces, van der Waals interactions and/or other attractive forces.These agglomerates are then processed in further processes, for exampleseparated from other components and/or the solution or dispersion. Afterthis treatment, the agglomerates are then separated again, i.e.deagglomerated, so that the surface-functionalized particles and theother particles, substances, materials, etc., are again presentseparately (deagglomeration). Examples of agglomeration-deagglomerationcycles which are preferred according to the invention are chemical orbiological test methods or separation processes, decontamination of(heavy metal-)contaminated earth, water purification, recycling ofelectrical/electronic scrap or gravity separation.

In chemical or biological test methods or separation processes, use ismade of, for example, specifically modified magnetic nanoparticles whichhave anchor groups for a specific antigen or virus, e.g. borrelia, HIV,hepatitis, on their surface. These specific anchor groups correspond, inparticular, to the abovementioned group R¹ which has a structurecorresponding to the respective separation or test task, for example asa result of the presence of the abovementioned functional groups.Bonding of these antigens/viruses to the modified particle surface(agglomeration) enables these constituents to be separated off from asolution by means of magnetic separation and thus detected. Thefunctionalized magnetic particles are then recycled by means ofsurfactants which again release the electrostatic, adhesive or van derWaals interaction between functionalized magnetic particle andantigen/virus (deagglomeration). In this way, the functionalizedmagnetite particles produced in an elaborate way can be reused.

The modified particles of the invention, in particular magneticparticles, can be used in water purification. Here, for example, it ispossible to use functionalized magnetite particles which remove organicconstituents, suspended materials or fat droplets from the water byeffecting hydrophobic agglomeration between the functionalized magnetiteparticle and the hydrophobic contaminant. These hydrophobic agglomeratescan be separated off by magnetic separation. In order that waterpurification is economical, it is useful to “unload” the hydrophobicmagnetite particles from the contaminant again and return them to thecircuit. This “unloading” can once again be affected by deagglomerationusing a specific surface-active substance (surfactant) and/or by meansof a specific solvent or solvent mixture.

Recycling of electrical/electronic scrap can, for example, be carriedout by magnetic recovery of materials of value (Ir, Pt, Ru) fromelectrical/electronic scrap, once again preferably using modifiedmagnetite particles which, after hydrophobicization of the materials ofvalue to be separated, can agglomerate with these and be separated off.After the agglomerates have been separated off, they are deagglomeratedagain so that the modified magnetic particles can be reused.

A further example is gravity separation, e.g. by means of cyclones knownto those skilled in the art. In this way, relatively dense constituentscan be separated off from less dense constituents by means of a gravityseparation. If the densities of the individual components differ onlyslightly, e.g. Pt-doped hematite and undoped hematite, the density ofthe component to be separated off can be increased by agglomeration witha further component. Here, for example, the Pt-doped hematite componentis hydrophobicized according to the invention to give modifiedparticles, so that addition of hydrophobicized barium sulfate gives anagglomerate of the modified hematite and barium sulfate which has agreater density difference from the undoped hematite. After theagglomerate has been separated off, it can be deagglomerated again.

The present invention therefore also preferably provides for the useaccording to the invention in which the agglomeration-deagglomerationcycle is a chemical or biological test method or separation process,water purification, purification of (heavy metal-) polluted earth,recycling of electrical/electronic scrap or gravity separation.

An advantage of the invention is that the particles which have beensurface-modified according to the invention are stable under theconditions prevailing in agglomeration and especially deagglomerationand can therefore preferably be reused.

EXAMPLES Example 1 General Methods Example 1.1 Repeated Treatment of theSolid with Surfactant Solution

10 g of solid are stirred in 1 l of a 0.2% strength by weight solutionof Lutensit A-ES from BASF SE (mixture of sodium alkylphenol ethersulfates) in water for 2 hours at room temperature. The solid issubsequently filtered off and washed with 1 l of water, 100 ml ofethanol and 100 ml of acetone. The filter cake is dried at 120° C. underreduced pressure for 4 hours. Samples are subsequently taken foranalysis. The remaining product is used for the renewed washing tests.

Example 1.2 Rapid Test for Ability to Float on Water

3 ml of water are placed in a 5 ml test tube. The solid to be examinedis subsequently carefully placed on the surface of the water by means ofa spatula. The solid in the test tube is subsequently observed to seewhether the solid sinks or remains afloat. In the case of floatingsolids, the closed vessel is shaken for 10 s. The solid in the test tubeis subsequently observed to see whether the solid floats again orremains under water.

Example 1.3 Contact Angle Measurement Contact Angle Measurement onPowders:

Contact angles are measured using a standard instrument (DropshapeAnalysis Instrument, Kruss DAS 10). A silhouette of the drop is recordedby means of a CCD camera and the drop shape is determined bycomputer-aided image analysis. The measurements are, unless indicatedotherwise, carried out as described in DIN 5560-2.

a) Production of a Homogeneous Powder Layer

The magnetite powder is applied as an appropriately 1 mm thick layeronto a 100 μm thick BASF Acronal V215 adhesive dispersion on a PET film.Using a spatula, the powder is pressed into the adhesive and excessmaterial which does not adhere is removed by shaking. Finally, remainingloose material is removed by blowing purified nitrogen under pressureover the specimen. This method gives a clean, homogeneous powder surfaceover the total area of the substrate of 75 mm×25 mm.

Powder surfaces normally display a certain roughness and contact angleor the measurement thereof are sensitive to this roughness. A directcomparison of the hydrophobicity can therefore be carried out only onpowders having the same particle size distribution and particle shape.Careful surfaces analyses using ToF-SIMS have shown that the surface ofthe powder layer produced by this method has no traces of adhesive andis representative of the powder.

b) Dynamic, Progressive Contact Angle Measurement

One milliliter of water is placed as a drop on the surface and 2 μl/minof water are continuously added. 20 μl of liquid volume are addedcontinuously in this way. Starting from a minimal volume of about 3 μl,contact angles are measured while the needle of the syringe used forintroduction remains in the drop. Contour measurements are carried outat a rate of about 0.5 Hz and are evaluated by means of a tangent methodin order to determine the contact angle directly at the three-phasecontact line. These contact angles are averaged over time, and fiveprogressive drops are measured at various positions for each sample andthe average value together with a standard deviation is determined.

Example 1.4 Recycling Experiments

An experiment is carried out on the use of magnetite hydrophobicizedaccording to the respective example as reusable carrier for thedecontamination of (heavy metal-) contaminated earth. For this purpose,3 g of magnetite were dispersed in a system comprising 100 g of a sandmixture (solids content: 1% by weight). This sand mixture comprises 99%by weight of inorganic siliceous constituents (e.g. feltspars, mica,iron pyrites) and 1% by weight of a specific hydrophobicized inorganicAs-comprising contaminant (Enargite). Hydrophobicization of thisinorganic contaminant is carried out using butylxanthate. After vigorousmixing of the hydrophobicized magnetite with this sand mixture, thearsenic component is separated off by means of hydrophobic flocculationwith the magnetite. The hydrophobic constituents are collected andtreated with a 0.1% strength by weight solution of a surfactant(Lutensit A-ES from BASF SE). In a subsequent magnetic separation step,the magnetic constituents are separated from the nonmagneticAs-comprising impurities. The hydrophobic magnetite is washed with a 1:1mixture of water and EtOH, filtered off and remixed with a freshlyproduced sand mixture. The process is repeated a total of ten times.

Example 2 Production of Hydrophobicized Magnetite Example 2.1 MagneticPigment 345 from BASF SE Silanized with ^(n)OctSi(OMe)₃ (According tothe Invention)

Synthesis: 10 g of magnetite pigment 345 (magnetiteFe^(II)(Fe^(III))₂O₄) from BASF SE are added to a solution of 370 mg of^(n)OctSi(OMe)₃ (97% strength, from ABCR) in 30 ml of toluene. 1 ml of25% strength acetic acid is then added to the solution. After 4 hoursunder reflux, the solid is filtered off and washed with 5 ml of acetoneand 1 l of distilled water. The product is dried overnight at 120° C.under reduced pressure. The dried product is, after preliminarycomminution, brushed through an analytical sieve (400 μm) and thusdeagglomerated and homogenized.

Analysis:

Floatation test: fresh solid and solid which has been washed ten timesfloat equally well on water (also after shaking under);

Elemental analysis: fresh: 0.12% of C, 0.06% of Si, washed ten times:0.12% of C, 0.06% of Si;

Contact angle: fresh 152°, washed ten times 146°;

Recycling test: When the yield of the As component is detected, theyield of 95% in the first cycle drops to only 91% in the tenth cyclewhen using the ^(n)OctSi(OMe)₃-silanized magnetic pigment 345 from BASFSE.

Example 2.2 ^(n)HexSi(OMe)₃-Silanized Magnetic Pigment 345 from BASF SE(According to the Invention)

Synthesis: The synthesis is carried out according to the schemedescribed in example 2.1. However, 330 mg of ^(n)HexSi(OMe)₃ (97%strength, from ABCR) are used as silanization reagent.

Analysis:

Floatation test: fresh solid and solid which has been washed ten timesfloat equally well on water (also after shaking under);

Elemental analysis: fresh: 0.08% of C, 0.05% of Si, washed ten times:0.07% of C, 0.05% of Si;

Contact angle: fresh 156°, washed ten times 152°

Example 2.3 ^(n)BuSi(OMe)₃-Silanized Magnetic Pigment 345 from BASF SE(According to the Invention)

Synthesis: The synthesis is carried out according to the schemedescribed in example 2.1. However, 290 mg of ^(n)BuSi(OMe)₃ (97%strength, from ABCR) are used as silanization reagent.

Analysis:

Floatation test: fresh solid and solid which has been washed ten timesfloat equally well on water (also after shaking under);

Elemental analysis: fresh: 0.06% of C, 0.05% of Si, washed ten times:0.07% of C, 0.05% of Si;

Contact angle: fresh 146°, washed ten times 133°;

Example 2.4 ^(n)OctSi(OMe)₃-Silanized Magnetic Pigment 345 from BASF SE(According to the Invention)

Synthesis: The synthesis is carried out according to the schemedescribed in example 2.1. However, water is used instead of toluene assolvent. This is brought to a pH of 3.5 by means of 25% strength aceticacid.

Analysis:

Floatation test: fresh solid and solid which has been washed ten timesfloat equally well on water (also after shaking under);

Elemental analysis: fresh: 0.10% of C, 0.06% of Si, washed ten times:0.10% of C, 0.04% of Si;

Contact angle: fresh 155°, washed ten times 148°;

Recycling test: When the yield of the As component is detected, theyield of 94% in the first cycle drops to only 92% in the tenth cyclewhen using the ^(n)OctSi(OMe)₃-silanized magnetic pigment 345.

Example 2.5 ^(n)OctSi(OMe)₃ Silanized Magnetic Pigment 345 of BASF SE(According to the Invention)

Synthesis: A solution of 370 mg ^(n)OctSi(OMe)₃ (97% by weight, ABCR) in5 mL water is adjusted to pH 3,5 with 25% by weight acidic acid andstirred for 60 minutes at room temperature. Afterwards, the solution issprayed onto 10 g magnetic pigment 345 (magnetite Fe^(II)(Fe^(III))₂O₄)of BASF SE, whereat the solid is constantly stirred. The product isdried at 120° C. for 2 hours in vacuum. Afterwards, the reaction iscompleted at 160° C. for 12 hours. The obtained product is primed afterpremilling through an analysis sieve (400 μm) and is therewithdeagglomerated and homogenized.

Analytic:

Floatation test: fresh solid and solid which has been washed ten timesfloat equally well on water (also after shaking under);

Contact angle: fresh 151°, washed ten times 154°.

Example 3 Comparative Examples Comparative Example 3.1 Commercial,Hydrophobic Magnetite Bayoxide E8707 H from Lanxess (not According tothe Invention)

Analysis:

Floatation test: fresh solid floats on water even after shaking under,while solid which has been washed twice no longer floats;

Elemental analysis: fresh: 0.10% of C, 0.05% of Si, washed ten times:0.03% of C, 0.01% of Si;

Contact angle: fresh 158°, washed ten times 116°

Recycling: Comparative tests using a previously hydrophobicizedmagnetite from Lanxess (product: Bayoxide E8707 H) display a dramaticloss in yield of over 40% after only the fourth cycle. The experimentsusing this product are then stopped.

Comparative Example 3.2 ^(n)OctMe₂SiCl-Silanized Magnetic Pigment 345from BASF SE (not According to the Invention)

Synthesis: Under a protective atmosphere, 10 g of magnetic pigment 345from BASF SE are suspended in 20 ml of toluene. The suspension is heatedto 70° C., and 0.3 g of ^(n)OctMe₂SiCl (97% strength, from ABCR) arethen added. The reaction mixture is subsequently maintained at 70° C.for 4 hours while stirring. The solid is subsequently filtered off,washed firstly with 50 ml of toluene, then 50 ml of methanol and finallywater until the washings are free of chloride. The product is dried at120° C. under reduced pressure for 4 hours. The dried product is, afterpreliminary comminution, brushed through an analytical sieve (400 μm)and thus deagglomerated and homogenized.

Analysis:

Floatation test: solid floats on water (even after shaking under), whilesolid washed once no longer floats on water;

Elemental analysis: fresh: 0.10% of C, 0.06% of Si, washed ten times:0.06% of C, 0,04% of Si;

Contact angle: fresh 148°, washed once 120°, washed ten times 98°

Comparative example 3.3 ^(n)BuMe₂SiCl-Silanized Magnetic Pigment 345from BASF SE (not According to the Invention)

Synthesis: The synthesis is carried out according to the schemedescribed in example 2.1. However, 0.3 g of ^(n)BuMe₂SiCl (97% strengthfrom ABCR) is used as silanization reagent.

Analysis:

Floatation test: solid floats on water (not after shaking under), whilesolid washed once no longer floats on water;

Elemental analysis: fresh: 0.09% of C, 0.06% of Si, washed ten times:0.03% of C, 0.02% of Si;

Contact angle: fresh 103°, washed ten times 89°

Comparative Example 3.4 Magnetic Pigment 345 from BASF SEHydrophobicized with Octylphosphonic Acid (not According to theInvention)

Synthesis: 8.0 kg of water are placed in an apparatus comprising a 12 lplastic bucket with spout as stirred vessel and a metal stirrer. 2 kg ofmagnetic pigment 345 from BASF SE are subsequently introduced and thestirring speed of the metal stirrer is selected so that the pigment doesnot sediment and air is also not drawn in (no head of foam is formed).12.5 g of n-octylphosphonic acid (OPA, 80% strength) from Albright &Wilson are subsequently added all at once and all the starting materialsare mixed in air at room temperature for 1.5 hours. After the end of thestirring time, the suspension is poured on to a porcelain filter (d=24cm with an MN 85/90 paper filter from Macherey-Nagel). Cracks formed inthe filter cake are wiped shut to improve the washing action. The solidis dried overnight at 110° C. in a convection drying oven. The driedproduct is, after preliminary comminution, brushed through an analyticalsieve (400 μm) and thus deagglomerated and homogenized.

Analysis:

Elemental analysis: 0.06% of P in the end product;

Recycling test: Even after the third cycle, only an unsatisfactory yieldof the As-comprising impurity of less than 50% is detected. Theexperiments are subsequently stopped.

1. A stable mixture comprising surface-modified particles which areobtained by reacting metal oxide or semimetal oxide particles with atleast one compound of the general formula (I)R¹ _(n)—Si(OR²)_(4-n)  (I) where R¹, R² and n have the followingmeanings: R¹ are each, independently of one another, hydrogen, linear orbranched, optionally functionalized C₁-C₃₀-alkyl, linear or branched,optionally functionalized C₂-C₃₀-alkenyl, linear or branched, optionallyfunctionalized C₂-C₃₀-alkynyl, optionally functionalizedC₃-C₂₀-cycloalkyl, optionally functionalized C₃-C₂₀-cycloalkenyl,optionally functionalized C₁-C₂₀-heteroalkyl, optionally functionalizedC₅-C₂₂-aryl, optionally functionalized C₆-C₂₃-alkylaryl, optionallyfunctionalized C₆-C₂₃-arylalkyl, optionally functionalizedC₅-C₂₂-heteroaryl, R² are each, independently of one another, hydrogen,linear or branched, optionally functionalized C₁-C₃₀-alkyl, linear orbranched, optionally functionalized C₂-C₂₀-alkenyl, linear or branched,optionally functionalized C₂-C₂₀-alkynyl, optionally functionalizedC₃-C₂₀-cycloalkyl, optionally functionalized C₃-C₂₀-cycloalkenyl,optionally functionalized C₁-C₂₀-heteroalkyl, optionally functionalizedC₅-C₂₂-aryl, optionally functionalized C₆-C₂₃-alkylaryl, optionallyfunctionalized C₆-C₂₃-arylalkyl, optionally functionalizedC₅-C₂₂-heteroaryl and/or group of the general formula (IIa)—SiR¹ _(m)(OR²)_(3-m)  (IIa) where R¹ and R² independently of oneanother have the above-mentioned meanings and m is independently of oneanother 0, 1, 2 or 3, n 1, 2 or 3, and at least one solvent, at leastone surface-active substance or a mixture thereof.
 2. The mixtureaccording to claim 1, wherein the mass ratio of solvent to modifiedparticle is greater than
 500. 3. The mixture according to claim 1,wherein n in the compound of the general formula (I) is 1 or 2,preferably
 1. 4. The mixture according to claim 1, wherein R² in thecompound of the general formula (I) or in the group of the generalformula (IIa) is methyl or ethyl.
 5. The mixture according to claim 1,wherein the at least one solvent is selected from the group consistingof aromatic hydrocarbons, alcohols, ethers, cyclic ethers, esters,cyclic esters, alkanes, cycloalkanes, olefins, cycloolefins, water andmixtures thereof.
 6. The mixture according to claim 1, wherein the atleast one surface-active substance is selected from the group consistingof nonionic, anionic, cationic and zwitterionic surfactants and mixturesthereof.
 7. The mixture according to claim 1, wherein the metal oxideused is an oxide of a metal selected from the group consisting of Mn,Fe, Co, Ni, Cu, combinations thereof and mixed oxides of these metalswith at least one alkaline earth metal.
 8. A process for treatingsurface-modified particles as defined in claim 1 with at least onesolvent, wherein the mass ratio of solvent to modified particle isgreater than
 500. 9. The method of using surface-modified particles asdefined in claim 1 in systems in which the modified particles arebrought into contact with at least one solvent, wherein the mass ratioof solvent to modified particle is greater than
 500. 10. The method ofusing surface-modified particles as defined in claim 1 inagglomeration-deagglomeration cycles.
 11. The method according to claim10, wherein the agglomeration-deagglomeration cycle is a chemical orbiological test method or separation process, decontamination of (heavymetal-)contaminated earth, water purification, recycling ofelectrical/electronic scrap or gravity separation.
 12. Process for thepreparation of a surface-modified particle as defined in claim 1 bycontacting the metal- or semi-metal oxide particle, which is to bemodified with a compound of general formula (I) or with polysiloxanes ofgeneral formula (I), comprising groups of general formula (IIa), asdefined in claim
 1. 13. Process according to claim 12, wherein thecontacting of the metal- or semi-metal oxide particle that is to bemodified with the compound of general formula (I) or with polysiloxanesof general formula (I), comprising groups of general formula (IIa) asdefined in claim 1, is conducted by spraying.
 14. Process according toclaim 12, wherein the reaction is accelerated by adjusting of thepH-value, preferably by addition of acid.
 15. Process according to claim12, wherein a temperature treatment is conducted after drying of theproducts, preferably at up to 160° C.
 16. Process according to claim 12,wherein the contacting is conducted by spraying the compounds of generalformula (I) or the polysiloxanes of general formula (I), comprisinggroups of general formula (IIa) as defined in claim 1, onto the metal-or semi-metal oxide particle that is to be modified.